LU503595B1

LU503595B1 - Heat-resistant steel hand welding rod for ultra-supercritical steel cb2 and fabrication method thereof

Info

Publication number: LU503595B1
Application number: LU503595A
Authority: LU
Inventors: Feng Guo; Feng Shao; Liang Chen
Original assignee: Suzhou Sitri Welding Tech Research Institute Co Ltd
Priority date: 2021-10-27
Filing date: 2022-07-11
Publication date: 2023-09-12
Also published as: WO2023071294A1; CN113857717A; CN113857717B; LU503595A1

Abstract

A heat-resistant steel hand welding rod for ultra-supercritical (USC) steel CB2 includes H08Cr9MoV alloy cored wire with low phosphorus and sulfur impurity contents and a flux coating wrapped around a surface of the cored wire. A deposited metal mainly includes 9% Cr, 1.5% Mo, 1% Co, 1% Ni, and 0.2% V, and trace alloying elements such as Nb, N, and B, such that the deposited metal for a welding seam has good mechanical properties after a heat treatment, especially impact energy performance, as an impact energy is higher than or equal to 47 J at normal temperature. After a heat treatment at 730°C to 740°C for 12 h, the deposited metal and a welded joint each have a tensile strength of 630 MPa to 750 MPa. The hand welding rod provides stable arcs, slight spattering, uniform welding slag coverage, good slag removal, allows all position welding with good welding performance.

Description

HEAT-RESISTANT STEEL HAND WELDING ROD FOR ULTRA-SUPERCRITICALU503595

STEEL CB2 AND FABRICATION METHOD THEREOF

TECHNICAL FIELD

The present disclosure belongs to the technical field of welding rod fabrication, and relates to a heat-resistant steel hand welding rod for ultra-supercritical (USC) steel CB2 and a fabrication method thereof. In particular, the present disclosure relates to a heat-resistant steel hand welding rod for novel 620°C USC Cr-containing ferritic heat-resistant steel CB2 and a fabrication method thereof.

BACKGROUND

With the continuous development of China's economy, the demand for electric power is increasing, and with the continuous improvement of global awareness of environmental protection, the transformation of energy structure is inevitable. In this context, the task of

China's energy transformation has been very clear, which is to further adjust the energy structure, develop clean energy, accelerate the development and utilization of clean energy, and construct new electric power systems based on new energy (that is, the development of new energy systems such as hydropower systems, wind power systems, and photovoltaic power systems).

In addition, the utilization of clean energy (natural gas power generation) is also an important part of China's energy supply. The gas turbine combined cycle (GTCC) with a natural gas as a fuel is a high-efficiency and low-pollution power generation mode, and has advantages such as high power supply efficiency, low investment, short construction period, flexible start-stop, high operation automation degree, and low pollution. Since a gas turbine is a core of a power plant, the research and application of materials for gas turbines are also constantly developing.

Steel CB2 is a material developed in the COSTS22 Action of the European Union. The

COSTS22 Action is a new initiative of the European Union in the field of advanced power generation technologies, namely, "Power Generation in the Twenty-First Century: High- efficiency and Low-pollution Power Plants", and the COST522 Action builds on the success of the COSTS01 Action. A steam turbine material for a power plant that allows a maximum inlet steam temperature of 650°C, a combustion chamber temperature of 1,450°C, and a NOx emission of less than 0.001% has been developed. Main alloy elements of this series of heat- resistant steels are shown in the following table:

Major ; LU503595

Li | rere fe] 8-95 <0.4 0.03-0.07

P91 0.12 0.6 1.05 0.25

Le | [oe oe ee er 03-06 | <04 0.03-0.07

P92 0.13 0.6 9.5 0.25 2.0

Steel 0.8- 9.0- 0.18- 0.015- 0.9-

EIERN

Studies have shown that CB2 materials have good heat conduction, a low coefficient of thermal expansion (CTE), excellent strength and toughness indexes, and excellent high- temperature creep performance and high-temperature oxidation resistance, and are currently recognized as ideal materials for 620°C USC unit castings. Steel CB2 is mainly used for core castings such as high-pressure and medium-pressure inner cylinders, nozzle chambers, and main steam valves of steam turbines under USC steam parameters. In developed countries, the application of welding materials corresponding to steel CB2 has been studied deeply and the welding materials have been commercially produced. In recent years, such a steel casting material has also been successfully developed through continuous efforts in China, with a

Chinese Grade of ZG12Cr9Mo1Co1N1VNbNB; and the development and application of a corresponding welding material have been started.

At present, a supporting welding rod for steel CB2 is also disclosed in China, where a welding core with a similar composition to steel CB2 is used for production, and mainly includes the following components: 9% Cr, 1% Mo, and 1% Co. However, the addition of cobalt to a cored wire will affect the manufacturing of a wire rod of the cored wires. Cobalt is easily precipitated during a steelmaking process to produce a hard and brittle metal compound, which deteriorates the mechanical properties of an intermetallic compound (IMC); and cobalt has an adverse effect on elongation and section shrinkage, and it is difficult to roll a wire rod or a qualification rate of wire rods during quality control is low, which increases a manufacturing cost of an alloy cored wire.

In addition, in China, for the 9% Cr-containing high-alloy steel hand welding rod products, an HO8A wire with low phosphorus and sulfur impurity contents is generally used as a cored wire, and a large number of alloy raw materials such as metal chromium, ferromolybdenum, a nickel powder, and ferrovanadium are added to a flux coating for the transition of an alloy. The addition of the large number of alloy raw materials in different proportions may lead to the non- thorough mixing of raw materials during a production process, resulting in uneven distribution of components of a deposited metal in a final hand welding rod product. In addition, the additidnu503595 of the large number of alloy raw materials in different proportions will make a manufacturing process of a hand welding rod difficult and also will make a cutting diameter of a final hand welding rod relatively large, and the large diameter will lead to poor welding process performance.

At present, China mainly relies on the import of such welding materials. The imported welding materials have a high price, a long ordering cycle, and inadequate after-sales service.

SUMMARY

In order to solve the above problems, the present disclosure provides a heat-resistant steel hand welding rod for USC steel CB2. A special HO8Cr9MoV alloy cored wire with low phosphorus and sulfur impurity contents is used for transition of major alloying elements to avoid the uneven distribution of components in the hand welding rod. A manufacturing process of the hand welding rod is relatively easy. With the specification ® 4.0 mm as an example, a cutting diameter of a hand welding rod is about ® 6.5 mm, and the hand welding rod with this diameter has good operational processability. The special HO8Cr9MoV alloy cored wire is developed and manufactured by Jiangsu Yonggang Group Co., Ltd. In addition, a flux coating is fabricated by uniformly mixing various raw materials such as marble, fluorite, and rutile.

Weight percentages of the raw materials in the flux coating can be adjusted to allow stable electric arcs during a welding process, slight spattering, beautiful welding seams, good welding slag removal, and all position welding.

In order to achieve the above technical objective, the present disclosure adopts the following technical solutions: A heat-resistant steel hand welding rod for USC steel CB2 is provided, including an HO8Cr9MoV special alloy cored wire with low phosphorus and sulfur impurity contents and a flux coating.

A deposited metal for a welding seam mainly includes the following components: 9% Cr, 1.5% Mo, 1% Co, 1% Ni, and 0.2% V, and other trace alloying elements such as Nb, N, and B are also added, such that the deposited metal for the welding seam has good normal temperature stretching, bending, impact energy, and other process properties after a heat treatment. After a heat treatment at 730°C to 740°C for 12 h, the deposited metal has a tensile strength of 630

MPa to 750 MPa and a normal temperature impact energy of higher than or equal to 47 J; and a corresponding welded joint has a tensile strength of 630 MPa to 750 MPa and a normal temperature impact energy of higher than or equal to 47 J. The hand welding rod is particularly suitable for the welding of steel for a USC thermal power unit, especially for the welding of ferritic heat-resistant steel CB2.

A deposited metal of the welding rod includes the following chemical components: C: 0.1%4503595 to 0.15%; Mn: less than or equal to 0.6%; Si: less than or equal to 0.2%; P: less than or equal to 0.01%; S: less than or equal to 0.01%; Cr: 9.0% to 10.0%; Ni: less than or equal to 1.0%;

Mo: 1.2% to 2.0%; Co: 0.9% to 1.5%; Nb: 0.05% to 0.09%; V: 0.24% to 0.40%; N: 0.02% to 0.04%; B: 0.001% to 0.005%; and Fe and impurities: the balance.

Preferably, the deposited metal of the welding rod includes the following chemical components: C: 0.08% to 0.13%; Mn: less than or equal to 0.6%; Si: less than or equal to 0.2%;

P: less than or equal to 0.01%; S: less than or equal to 0.01%; Cr: 9.0% to 9.5%; Ni: less than or equal to 1.0%; Mo: 1.0% to 1.5%; Co: 0.9% to 1.5%; Nb: 0.05% to 0.09%; V: 0.24% to 0.40%; N: 0.02% to 0.04%; B: 0.001% to 0.005%; and Fe and impurities: the balance.

Preferably, the HO8CrOMoV special alloy cored wire is manufactured by Jiangsu Yonggang

Group Co., Ltd., and has a diameter deviation of + 0.4 mm.

Preferably, the HO8CrOMoV special alloy cored wire includes the following chemical components in mass percentage: C: 0.09% to 0.10%; Mn: 0.50% to 0.60%; Si: 0.15% to 0.20%;

P: less than or equal to 0.006%; S: less than or equal to 0.006%; Cr: 8.95% to 9.0%; Ni: 0.35% to 0.40%; Mo: 0.95% to 1.0%; Nb: 0.065% to 0.07%; V: 0.18% to 0.20%; N: 0.04% to 0.05%:

Al: less than or equal to 0.020%; Cu: less than or equal to 0.10%; As: less than or equal to 0.008%; Sn: less than or equal to 0.005%; Sb: less than or equal to 0.005%; Pb: less than or equal to 0.005%; Bi: less than or equal to 0.005%; and Fe: the balance.

Preferably, the flux coating is applied to an outer wall of the welding core; and the flux coating includes the following components in weight percentage: marble: 20% to 40%; fluorite: 15% to 30%; quartz powder: 7% to 9%; rutile: 4% to 9%; barium carbonate: 3% to 8%; metal chromium: 3.0% to 7.0%; cobalt powder: 2.0% to 6.0%, ferromolybdenum: 1.0% to 4.0%; electrolytic manganese: 1.0% to 2.0%; nickel powder: 1.0% to 3.5%; ferroniobium: 0.5%; ferrovanadium: 0.5%; ferrosilicon: 0.4%; ferrochrome nitride: 0.4%; soda ash: 0.5%; binder: 1.5%; rare-earth element (REE): 0% to 1%; and iron powder: the balance.

The marble includes: CaCOs as a main component: more than or equal to 97%, S: less than or equal to 0.03%, and P: less than or equal to 0.03%; and the marble meets the following particle size requirements: -40 mesh: more than or equal to 100%, -60 mesh: more than or equal to 97%, and -100 mesh: more than or equal to 80%; the fluorite includes: CaF, as a main component: more than or equal to 97%, S: less than or equal to 0.03%, and P: less than or equal to 0.03%; and the fluorite meets the following particle size requirements: -40 mesh: more than or equal to 100%, -60 mesh: more than or equal to 97%, and -100 mesh: more than or equal to 90%; the quartz powder includes: SiO; as a main component: more than or equal to 98%, S: less than or equal to 0.03%, and P: less than or equal to 0.01%; and the quartz powder meets th&J503595 following particle size requirements: -40 mesh: more than or equal to 100%, -60 mesh: more than or equal to 98%, and -100 mesh: more than or equal to 90%; the rutile includes: TiO; as a main component: more than or equal to 95%, S: less than or 5 equal to 0.03%, and P: less than or equal to 0.03%; and the rutile meets the following particle size requirements: -40 mesh: more than or equal to 100%, -60 mesh: more than or equal to 98%, and -100 mesh: more than or equal to 90%; the barium carbonate includes: BaCOs as a main component: more than or equal to 98%, S: less than or equal to 0.03%, and P: less than or equal to 0.03%; and the barium carbonate meets the following particle size requirements: -100 mesh: more than or equal to 100%, and -200 mesh: more than or equal to 95%; the metal chromium includes: Cr: more than or equal to 99.5%, C: less than or equal to 0.020%, S: less than or equal to 0.003%, and P: less than or equal to 0.01%; and the metal chromium meets the following particle size requirements: -60 mesh: more than or equal to 100%, and -100 mesh: more than or equal to 60%; the ferromolybdenum includes: Mo: 59.0% to 63.0%, Si: less than or equal to 1.6%, C: less than or equal to 0.06%, S: less than or equal to 0.050%, and P: less than or equal to 0.080%; and the ferromolybdenum meets the following particle size requirements: -60 mesh: more than or equal to 100%, and -100 mesh: more than or equal to 80%; the electrolytic manganese includes: Mn: more than or equal to 99.5%, C: less than or equal to 0.02%, S: less than or equal to 0.04%, and P: less than or equal to 0.01%; and the electrolytic manganese meets the following particle size requirements: -60 mesh: more than or equal to 100%, and -100 mesh: more than or equal to 80%; the nickel powder includes: Ni: more than or equal to 99.8%, C: less than or equal to 0.02%,

S: less than or equal to 0.003%, and P: less than or equal to 0.01%; and the nickel powder meets the following particle size requirements: -60 mesh: more than or equal to 100%, and -100 mesh: more than or equal to 80%; the cobalt powder includes: Co: more than or equal to 99.8%, C: less than or equal to 0.02%,

S: less than or equal to 0.003%, and P: less than or equal to 0.01%; and the cobalt powder meets the following particle size requirements: -60 mesh: more than or equal to 100%, and -100 mesh: more than or equal to 80%; the ferrosilicon includes: Si: 43.0% to 47.0%, C: less than or equal to 0.10%, S: less than or equal to 0.03%, and P: less than or equal to 0.03%; and the ferrosilicon meets the following particle size requirements: -60 mesh: more than or equal to 100%, and -100 mesh: more than or equal to 80%;

the ferrovanadium includes: V: 50.0% to 55.0%, Si: less than or equal to 2.0%, C: less than503595 or equal to 0.80%, S: less than or equal to 0.03%, and P: less than or equal to 0.06%; and the ferrovanadium meets the following particle size requirements: -60 mesh: more than or equal to 100%, and -100 mesh: more than or equal to 50%; the ferroniobium includes: Nb: 65.0% to 70.0%, S1: less than or equal to 1.0%, C: less than or equal to 0.15%, S: less than or equal to 0.050%, and P: less than or equal to 0.080%; and the ferroniobium meets the following particle size requirements: -60 mesh: more than or equal to 98%, and -100 mesh: more than or equal to 80%; the ferrochrome nitride includes: Cr: 57.0% to 63.0%, N: 7.0% to 8.5%, Si: less than or equal to 1.0%, C: less than or equal to 0.15%, S: less than or equal to 0.050%, and P: less than or equal to 0.080%; and the ferrochrome nitride meets the following particle size requirements: -60 mesh: more than or equal to 100%, and -100 mesh: more than or equal to 60%; the iron powder includes : Fe: more than or equal to 98%, C: less than or equal to 0.05%, S: less than or equal to 0.015%, and P: less than or equal to 0.03%, and has a bulk density of 3.0 + 0.1; and the iron powder meets the following particle size requirements: -60 mesh: more than or equal to 100%, and -100 mesh: more than or equal to 90%; the soda ash includes Na:CO; of more than or equal to 99%, and meets the following particle size requirements: -100 mesh: more than or equal to 100%, and -200 mesh: more than or equal to 98%; and the binder includes: Na:O: 9.5% to 13.0%, K: less than or equal to 0.050%, and ash: 20.0% to 30.0%; and the binder meets the following particle size requirements: -120 mesh: more than or equal to 100%, and -200 mesh: more than or equal to 50%, where the symbol "-" in front of a mesh represents passing through a sieve during screening, for example, "-100 mesh: more than or equal to 100%" means that a proportion of particles that pass through a 100-mesh sieve is greater than or equal to 100%, and "-60 mesh: more than or equal to 97%" means that a proportion of particles that pass through a 60-mesh sieve is greater than or equal to 97%.

The present disclosure provides a fabrication method of the heat-resistant steel hand welding rod for USC steel CB2, including: weighing the components of the flux coating according to the proportions, and uniformly mixing the components; adding water glass at a weight of 14% to 28% based on a total weight of the components of the flux coating, uniformly stirring a resulting mixture in a wet state, and pressing the mixture into a cake; transferring the cake to a coating machine, and wrapping the cake around the special alloy cored wire; and baking a resulting article at 60°C to 100°C for 1 h and then at 350°C to 380°C for 1 h, furnace- cooling to 100°C to 150°C, and taking out the article.

Preferably, the water glass includes potassium and sodium in a ratio of 1:1. As a binder, th&J503595 water glass can play an arc-stabilizing role to some extent as it includes both K and Na.

Generally, a type of the water glass can be determined according to the composition of the flux coating.

Reasons for setting dosage ranges for chemical elements in the deposited metal of the present disclosure are as follows.

In the present disclosure, a C content in a specified range can increase strength of steel.

However, when the C content is high, the long-term action of stress at a high temperature will accelerate the depletion of alloying elements in a solid solution and the significant aggregation of carbide phases, thereby reducing the thermal strength performance of steel and increasing the brittleness of steel. Therefore, in order to ensure the thermal strength performance of a material at a high temperature and also ensure the impact toughness, it is necessary to control the carbon content at 0.08% to 0.13%.

Mn is an excellent deoxidizer and desulfurizer. When a welding seam includes a specified amount of manganese, the hot brittleness caused by sulfur can be eliminated or weakened. In addition, manganese at a specified content will improve the stability of a high-temperature ferrite of organization. However, in order to avoid the regeneration of austenite in a welding seam at the highest post-weld heat treatment (PWHT) temperature, it is necessary to control the

Mn content appropriately at 0.6% or lower.

Si is an important deoxidizer, and when Si and Cr coexist, the oxidation resistance of an alloy can also be improved. In the heat-resistant steel, a relatively low Si content is conducive to the improvement of impact toughness of the deposited metal, and in order to consider both high-temperature oxidation resistance and high-temperature corrosion resistance of the material, the Si content in the welding material is controlled at 0.3% or less.

S is a harmful element. At a high welding temperature, FeS and molten iron can be infinitely miscible, but when a furnace hearth solidifies, FeS reacts with Fe or FeO to produce a low- melting-point eutectic, which will cause crystalline cracks in a welding seam. Therefore, the S content needs to be strictly controlled at less than or equal to 0.01%.

P is a harmful element. P will seriously reduce the plasticity and impact toughness of the material, and because P will be segregated in the steel, the tempering brittleness of the steel will be increased. Therefore, the P content needs to be strictly controlled at less than or equal to 0.01%.

Cr can improve the high-temperature oxidation resistance and high-temperature corrosion resistance of the heat-resistant steel and improve the high-temperature endurance strength and creep resistance of steel, and at a high temperature of 620°C, the solid solution treatment of chromium into a matrix at a content of about 9% can play an excellent solid soluti®n)503595 strengthening role. Therefore, the Cr content is controlled at 9% to 9.5%.

Ni can improve the impact toughness of the deposited metal and can also reduce the sensitivity of 6 ferrite formation, and the presence of the & ferrite is detrimental to the performance of the deposited metal. An appropriate nickel content is beneficial. A too high nickel content will affect the creep resistance of the material and will also excessively reduce an Acl temperature of the deposited metal, such that the Acl temperature may be lower than the PWHT temperature, which will lead to the generation of a new untempered martensite structure after cooling. Therefore, the Ni content is generally controlled at 1% or less.

Mo is an important alloying element to improve the high temperature creep resistance of the heat-resistant steel. At a high temperature of 620°C or lower, a Mo content is about 1%, which is beneficial to the long-term creep resistance while maintaining good impact toughness.

Therefore, the Mo content is controlled at 1.0% to 1.5%.

Co favors the generation of a martensite matrix and inhibits the generation of a Ô ferrite. A test is conducted by adding the cobalt powder raw material in different proportions, and test results show that the tensile strength of the full deposited metal increases with the increase of a

Co content, and the elongation first increases and then decreases. This is because the addition of Co reduces the stacking fault energy (SFE) of the material to make the solid solution strengthening role well played, and improves the plastic deformation resistance of the material to improve the yield strength and tensile strength of the material. In addition, experimental studies have shown that a specified content of Co facilitates the high-temperature long-term creep resistance while maintaining good impact toughness. Therefore, comprehensively, the cobalt content is controlled at 0.9% to 1.5%.

Nb is a strong carbide-forming element, and Nb can be fixed with carbon in the form of

NbC to improve the high-temperature strength of a welding seam. However, a too high Nb content easily leads to grain-boundary cracks, and will also reduce the impact toughness.

Therefore, the Nb content is controlled at 0.05% to 0.09%.

V is a strong carbide-forming element, and V added to the steel can form a fine and stable alloy carbide with carbon to improve the high-temperature endurance strength of a welding seam. However, a too high V content easily leads to grain-boundary cracks. Therefore, the V content is controlled at 0.24% to 0.40%.

Under the action of V, N has a positive effect on the high-temperature creep resistance, but a too high N content will greatly reduce the toughness of the material. Therefore, the N content is controlled at 0.02% to 0.04%.

The addition of an appropriate amount of B to the steel can refine the grains, improve the compactness of the steel, and increase the thermal strength. A too high B content easily lead$)503595 to large-size boron-containing inclusions during a cooling and solidification process, resulting in welding seam cracking. Therefore, the B content is controlled at 0.001% to 0.005%.

The REE can purify the deposited metal, and the REE is a beneficial element for well deoxidization, desulfurization, and removal of other harmful impurities, which can refine the grains and improve the oxidation resistance and creep resistance of the material.

The rest elements are Fe and other trace elements.

Main functions of the components in the flux coating of the present disclosure are as follows.

The marble includes CaCO; as a main component, which has functions of slag-forming and gas-generating and also has the effects of dephosphorization and desulfurization during a metallurgical process. CaO, a decomposition product of CaCO; during a welding process, is a basic oxide, which can improve the alkalinity of a slag. A weight proportion of CaO in the flux coating can adjust a viscosity of the slag, thereby affecting the slag removal of a welding seam.

The fluorite includes CaF, as a main component. The fluorite can effectively remove H, reduce the melting point and viscosity of a slag, and improve the wettability of the furnace hearth. The fluorite will be decomposed during a welding process to produce a harmful gas hydrogen fluoride, resulting in poor arc stability and increased spattering. Therefore, a fluorite content must be strictly controlled.

The quartz powder includes SiO; as a main component, and is also a slag-forming agent.

The quartz powder can improve the wettability of a liquid metal and make a welding bead formed beautifully. An appropriate amount of the SiO, or quartz powder can lead to good slag removal performance.

The rutile includes TiO; as a main component, and the rutile mainly serves as a slag-forming agent and an arc-stabilizing agent, which can improve the slag removal of a welding seam, thereby resulting in beautiful welding seams, excellent slag coverage, and slight spattering.

The barium carbonate includes BaCO; as a main component, a decomposition product of the barium carbonate has functions of slag-forming and gas-generating, and a solidification form of a slag can be adjusted during a welding process to improve the slag removal of a welding seam.

The penetration of the metal chromium, electrolytic manganese, nickel powder, cobalt powder, and chromium nitride into the alloy is mainly intended to compensate a burn loss of alloying elements during a welding process, and an alloy composition in a welding seam is adjusted to improve a structure of the welding seam, thereby improving the mechanical properties of the welding seam.

The soda ash includes Na,COs as a main component, and mainly plays a lubricating rol&J503595 during a manufacturing process, which makes the welding rod easily fabricated and avoids large eccentricity.

The present disclosure has the following beneficial effects. (1) The use of the HO8Cr9MoV special alloy cored wire with low phosphorus and sulfur impurity contents can uniformly transit the main alloying elements into a deposited metal of a welding seam, such that components of the welding seam are uniformly distributed, have stable performance, and will not undergo alloy segregation. The other trace alloying elements of the present disclosure can be added through microalloying of the components of the flux coating, such that the uniformity of alloy transition is stabilized and the performance is stabilized, which not only reduces the complexity of smelting of the alloy cored wire, but also meets the performance requirements matching the steel CB2. The alloy cored wire used in the present disclosure is currently at a specified sales scale in China, and a manufacturing cost of the cored wire is relatively low. (2) In terms of supporting welding materials for steel CB2, it is necessary to study the influence of contents of elements such as nitrogen, nickel, cobalt, and boron in the deposited metal on the mechanical properties of a welding seam, especially considering the requirements of impact toughness.

Nitrogen reacts with carbon to produce a carbon nitride, and in the subsequent heat treatment, nitrogen can increase the strength value through dispersion strengthening with other elements, but a too high nitrogen content will reduce the plasticity and toughness of a deposited metal. Therefore, it is necessary to control a nitrogen content range.

The addition of nickel can significantly improve the toughness of a welding seam, but the increase of nickel and manganese will reduce an Acl temperature of a deposited metal, and the

Acl temperature is a reference temperature for the highest PWHT temperature. Therefore, it is necessary to control a nickel content range. For the welding material of the hand welding rod corresponding to steel CB2, test results show that the increase of nickel and manganese contents in a deposited metal, the impact value will increase, but the high-temperature endurance strength will decrease. This is because nickel and manganese are austenitic elements, and with the increase of nickel and manganese contents, a new austenitic phase will be generated during heat treatment and will be transformed into an untempered martensite structure during cooling.

Therefore, in order to comprehensively consider the low-temperature impact toughness of a deposited metal and achieve the high-temperature endurance strength, it is necessary to strictly control the nickel and manganese contents in the deposited metal.

The addition of cobalt can improve the high-temperature strength of a welding seam, favor the generation of a martensite matrix, and inhibit the generation of a 6 ferrite. À test is conducted)503595 by adding the cobalt powder raw material in different proportions, and test results show that the tensile strength of the full deposited metal increases with the increase of a Co content, and the elongation first increases and then decreases. This is because the addition of Co reduces the

SFE of the material to make the solid solution strengthening role well played, and improves the plastic deformation resistance of the material to improve the yield strength and tensile strength of the material. In addition, experimental studies have shown that a specified content of Co facilitates the high-temperature long-term creep resistance while maintaining good impact toughness. Therefore, comprehensively, a cobalt content is controlled at 0.7% to 1.5%.

The addition of boron can improve the heat durability and high-temperature creep resistance of the steel, and has the effect of grain refinement. However, a too high boron content will increase the hot cracking tendency of a welding seam and affect the impact toughness.

Therefore, it is necessary to control a boron content. (3) The weight proportions of components in the flux coating of the welding rod of the present disclosure can be adjusted to make the welding rod have good operating performance, which not only ensures the technical requirements of welding, but also meets the mechanical property requirements of a welding seam. The use of a hand welding rod with such a slag structure can lead to stable arcs, slight spattering, beautiful welding seams, and good welding slag removal during a welding process, and more importantly, it allows all position welding. (4) The flux coating of the welding rod of the present disclosure has a moisture content of lower than 0.15%, and the deposited metal has a diffusible hydrogen content of lower than 4 mL/100 g (mercury method). (5) The deposited metal for the hand welding rod of the present disclosure mainly includes the following components: 9% Cr, 1.5% Mo, 1% Co, 1% Ni, and 0.2% V, and other trace alloying elements are also added to achieve good welding process performance. After a heat treatment at 730°C to 740°C for 12 h, the deposited metal for a welding seam has a tensile strength of 630 MPa to 750 MPa and a normal temperature impact energy of higher than or equal to 47 J; and after a heat treatment at 730°C to 740°C for 12 h, a corresponding welded joint has a tensile strength of 630 MPa to 750 MPa and a normal temperature impact energy of higher than or equal to 47 J. In the present disclosure, the ratio designs of alloying components and welding slag components are optimized to obtain good mechanical properties such as tensile strength and impact toughness and excellent operating performance of all position welding, which is particularly suitable for the welding of steel for a USC thermal power unit, especially for the welding of USC steel CB2.

BRIEF DESCRIPTION OF THE DRAWINGS LU503595

FIG. 1 shows pictures of on-site welding by the welding rod of the present disclosure, where

A is a schematic diagram illustrating a size of a welding groove, and B to E are pictures illustrating a welding process for test plates.

FIG. 2 is a schematic diagram of a sleeve for the hand welding rod.

DETAILED DESCRIPTION OF THE EMBODIMENTS Examples:

Components of the special alloy cored wire used in each example for the heat-resistant steel hand welding rod for USC steel CB2 in the present disclosure were shown in Table 1.

Table 1 (Weight Percentage) esse [ee

Example 0.092 | 0.17 | 0.55 | 0.005 | 0.002 | 8.98 | 0.38 | 0.98 | 0.065 | 0.18 | 0.042 1

Example > 0.093 | 0.16 | 0.54 | 0.006 | 0.003 0.37 1 0.065 | 0.19 | 0.042

Example ; 0.092 | 0.17 | 0.54 | 0.005 | 0.003 0.38 1 0.065 | 0.18 | 0.04

À formula of a welding flux for the heat-resistant steel hand welding rod for USC steel CB2 in each example of the present disclosure was shown in Table 2.

Table 2 (Weight Percentage)

Electrolyti

Marbl | Fluorit Quartz Rutil Barium Metal Ferromolybdenu c € € powder we carbonate chromium m manganes € 28 18 5 4 5,5 3 1.5 el 35 24 5 54 3.2 1.4 e2 22 7 7 4 5,5 3.1 1.3 e 3

Ferrochro | Ferroniobiu | Ferrovanadiu | Ferrosilico powde | powde oo Soda ash Binder me nitride m m n r r

Exampl €

When the heat-resistant steel hand welding rod for USC steel CB2 fabricated by the method was used, components of a deposited metal were shown in Table 3 (wt%).

Table 3 (Weight Percentage)

M cfs] fox Ole en

Exampl | 0.10 | 0.1 | 0.5 | 0.00 | 0.00 | 9. | 0.3 0.2 | 0.03 | 0.00

TY

Exampl 0.1 | 0.5 | 0.00 | 0.00 | 9. |03 1.1 0.3 | 0.03 | 0.00 en FIRS TY en [TT [en 0.11 14] 1.1 0.03 e 3 6 4 5 3 3 8 9 4

The components of the flux coating were weighed according to the proportions and uniformly mixed; a binder water glass was added at a weight 20% of a total weight of the components of the flux coating, and a resulting mixture was uniformly stirred in a wet state and pressed into a cake; the cake was transferred to a coating machine and wrapped around the special alloy cored wire; and a resulting article was baked at 80°C for 1 h and then at 350°C for 1 h, furnace-cooled to 120°C, and taken out.

When the heat-resistant steel hand welding rod for USC steel CB2 fabricated by the method was used, mechanical properties of the deposited metal were shown in Table 4.

Table 4 (Mechanical Properties)

Yield Tensile Impact value strength strength Flongation (Normal PWHT (MPa) (MPa) si temperature) J

Few | wo | a | w= re

It can be seen from the data in Tables 3 and 4 that, when the heat-resistant steel hand welding rod for USC steel CB2 in the present disclosure is used, components and mechanical properties of a deposited metal are suitable for welding of USC steel CB2.

When the heat-resistant steel hand welding rod for USC steel CB2 fabricated by the method was used, a diffusible hydrogen content of a deposited metal was shown in Table 5 below. LU503595

Table 5 (Diffusible Hydrogen Content: mL/100 g)

Table 6 Welding parameters

Welding current (A)

Flat welding and vertical welding each were conducted according to the welding parameters in Table 6 to test the process performance of the hand welding rod. If an arc can burn continuously without breaking and does not undergo drifting or flickering, it is determined that the arc stability is good; and on the contrary, it is determined that the arc stability is poor.

For the evaluation of spattering, if no large metal particle is spattered during a welding process and spattered particles have a diameter of less than 2 mm, it is determined that the spattering is slight; and on the contrary, it is determined that the spattering is heavy.

For the evaluation of slag removal, if the slag can be automatically removed or completely removed by knocking with a 1 kg iron hammer from a back of a fillet weld test plate, it is determined that the slag removal is good; and on the contrary, it is determined that the slag removal is poor. For the evaluation of slag coverage, if the slag can completely and uniformly cover a surface of a welding bead, it is determined that the slag coverage is good; and on the contrary, it is determined that the slag coverage is poor. For the evaluation of welding seam forming, if the transition between a welding seam and workpieces is smooth, a smooth welding seam is formed, and a welding bead of vertical welding does not fall, it is determined that the welding seam forming is good; and on the contrary, it is determined that the welding seam forming is poor.

Table 7 Flat welding process performance

Welding coverage forming

Table 8 Vertical welding process performance

Welding LU503595 removal coverage forming

Finally, it can be seen from the pictures of on-site welding by the welding rod of the present disclosure in FIG. 1 and the schematic diagram of the sleeve of the hand welding rod in FIG. 2 that, when the heat-resistant steel hand welding rod of the present disclosure is used for the welding of steel CB2, a welding seam is beautiful, a slag is completely removed during a welding process, the welding sleeve has a moderate length, and the welding process performance is good.

Although the examples of the present disclosure have been illustrated, it should be understood that those of ordinary skill in the art may still make various changes, modifications, replacements, and variations to the above examples without departing from the principle and spirit of the present disclosure, and the scope of the present disclosure is limited by the claims and legal equivalents thereof.

Claims

CLAIMS LU503595

1. À heat-resistant steel hand welding rod for ultra-supercritical steel CB2, comprising a special HO8Cr9MoV alloy cored wire and a flux coating wrapped around a surface of the cored wire, characterized in that a deposited metal of the welding rod comprises the following chemical components: C:

0.1% to 0.15%; Mn: less than or equal to 0.6%; Si: less than or equal to 0.2%; P: less than or equal to 0.01%; S: less than or equal to 0.01%; Cr: 8.5% to 10.0%; Ni: less than or equal to

1.0%; Mo: 1.0% to 2.0%; Co: 0.7% to 1.5%; Nb: 0.02% to 0.09%; V: 0.15% to 0.40%; N: 0.02% t0 0.06%; B: 0.001% to 0.005%; and Fe and impurities: the balance.

2. The heat-resistant steel hand welding rod for ultra-supercritical steel CB2 according to claim 1, characterized in that the deposited metal of the welding rod comprises the following chemical components: C: 0.08% to 0.13%; Mn: less than or equal to 0.6%; Si: less than or equal to 0.2%; P: less than or equal to 0.01%; S: less than or equal to 0.01%; Cr: 9.0% to 9.5%; Ni: less than or equal to 1.0%; Mo: 1.0% to 1.5%; Co: 0.9% to 1.5%; Nb: 0.05% to 0.09%; V: 0.24% to 0.40%; N: 0.02% to 0.04%; B: 0.001% to 0.005%; and Fe and impurities: the balance.

3. The heat-resistant steel hand welding rod for ultra-supercritical steel CB2 according to claim 1, characterized in that the special HO8Cr9MoV alloy cored wire has a diameter deviation of + 0.4 mm; and the special HO8CrOMoV alloy cored wire comprises the following chemical components in mass percentage: C: 0.09% to 0.10%; Mn: 0.50% to 0.60%; Si: 0.15% to 0.20%; P: less than or equal to 0.006%; S: less than or equal to 0.006%; Cr: 8.95% to 9.0%; Ni: 0.35% to 0.40%; Mo: 0.95% to 1.0%; Nb: 0.065% to 0.07%; V: 0.18% to 0.20%; N: 0.04% to 0.05%; Al: less than or equal to 0.020%; Cu: less than or equal to 0.10%; As: less than or equal to 0.008%; Sn: less than or equal to 0.005%; Sb: less than or equal to 0.005%; Pb: less than or equal to 0.005%; Bi: less than or equal to 0.005%; and Fe: the balance.

4. The heat-resistant steel hand welding rod for ultra-supercritical steel CB2 according to claim 1, characterized in that the flux coating comprises the following components in weight percentage: marble: 20% to 40%; fluorite: 15% to 30%; quartz powder: 7% to 9%; rutile: 4% to 9%; barium carbonate: 3% to 8%; metal chromium: 3.0% to 7.0%; cobalt powder: 2.0% to

6.0%; ferromolybdenum: 1.0% to 4.0%; electrolytic manganese: 1.0% to 2.0%; nickel powder:

1.0% to 3.5%; ferroniobium: 0.5%; ferrovanadium: 0.5%; ferrosilicon: 0.4%; ferrochrome nitride: 0.4%; soda ash: 0.5%; binder: 1.5%; rare-earth element: 0% to 1%; and iron powder: the balance.

5. The heat-resistant steel hand welding rod for ultra-supercritical steel CB2 according 14503595 claim 4, characterized in that the marble comprises: CaCO; as a main component: more than or equal to 97%, S: less than or equal to 0.03%, and P: less than or equal to 0.03%; and the marble meets the following particle size requirements: -40 mesh: more than or equal to 100%, -60 mesh: more than or equal to 97%, and -100 mesh: more than or equal to 80%; the fluorite comprises: CaF; as a main component: more than or equal to 97%, S: less than or equal to 0.03%, and P: less than or equal to 0.03%; and the fluorite meets the following particle size requirements: -40 mesh: more than or equal to 100%, -60 mesh: more than or equal to 97%, and -100 mesh: more than or equal to 90%; the quartz powder comprises: SiO; as a main component: more than or equal to 98%, S: less than or equal to 0.03%, and P: less than or equal to 0.01%; and the quartz powder meets the following particle size requirements: -40 mesh: more than or equal to 100%, -60 mesh: more than or equal to 98%, and -100 mesh: more than or equal to 90%; the rutile comprises: TiO; as a main component: more than or equal to 95%, S: less than or equal to 0.03%, and P: less than or equal to 0.03%; and the rutile meets the following particle size requirements: -40 mesh: more than or equal to 100%, -60 mesh: more than or equal to 98%, and -100 mesh: more than or equal to 90%; the barium carbonate comprises: BaCOs as a main component: more than or equal to 98%, 20S: less than or equal to 0.03%, and P: less than or equal to 0.03%; and the barium carbonate meets the following particle size requirements: -100 mesh: more than or equal to 100%, and - 200 mesh: more than or equal to 95%; the metal chromium comprises: Cr: more than or equal to 99.5%, C: less than or equal to

0.020%, S: less than or equal to 0.003%, and P: less than or equal to 0.01%; and the metal chromium meets the following particle size requirements: -60 mesh: more than or equal to 100%, and -100 mesh: more than or equal to 60%; the ferromolybdenum comprises: Mo: 59.0% to 63.0%, Si: less than or equal to 1.6%, C: less than or equal to 0.06%, S: less than or equal to 0.050%, and P: less than or equal to 0.080%; and the ferromolybdenum meets the following particle size requirements: -60 mesh: more than orequal to 100%, and -100 mesh: more than or equal to 80%; the electrolytic manganese comprises: Mn: more than or equal to 99.5%, C: less than or equal to 0.02%, S: less than or equal to 0.04%, and P: less than or equal to 0.01%; and the electrolytic manganese meets the following particle size requirements: -60 mesh: more than or equal to 100%, and -100 mesh: more than or equal to 80%; the nickel powder comprises: Ni: more than or equal to 99.8%, C: less than or equal to

0.02%, S: less than or equal to 0.003%, and P: less than or equal to 0.01%; and the nickeU503595 powder meets the following particle size requirements: -60 mesh: more than or equal to 100%, and -100 mesh: more than or equal to 80%; the cobalt powder comprises: Co: more than or equal to 99.8%, C: less than or equal to

0.02%, S: less than or equal to 0.003%, and P: less than or equal to 0.01%; and the cobalt powder meets the following particle size requirements: -60 mesh: more than or equal to 100%, and -100 mesh: more than or equal to 80%; the ferrosilicon comprises: Si: 43.0% to 47.0%, C: less than or equal to 0.10%, S: less than or equal to 0.03%, and P: less than or equal to 0.03%; and the ferrosilicon meets the following particle size requirements: -60 mesh: more than or equal to 100%, and -100 mesh: more than or equal to 80%; the ferrovanadium comprises: V: 50.0% to 55.0%, Si: less than or equal to 2.0%, C: less than or equal to 0.80%, S: less than or equal to 0.03%, and P: less than or equal to 0.06%; and the ferrovanadium meets the following particle size requirements: -60 mesh: more than or equal to 100%, and -100 mesh: more than or equal to 50%; the ferroniobium comprises: Nb: 65.0% to 70.0%, Si: less than or equal to 1.0%, C: less than or equal to 0.15%, S: less than or equal to 0.050%, and P: less than or equal to 0.080%; and the ferroniobium meets the following particle size requirements: -60 mesh: more than or equal to 98%, and -100 mesh: more than or equal to 80%; the ferrochrome nitride comprises: Cr: 57.0% to 63.0%, N: 7.0% to 8.5%, Si: less than or equal to 1.0%, C: less than or equal to 0.15%, S: less than or equal to 0.050%, and P: less than or equal to 0.080%; and the ferrochrome nitride meets the following particle size requirements: -60 mesh: more than or equal to 100%, and -100 mesh: more than or equal to 60%; the iron powder comprises: Fe: more than or equal to 98%, C: less than or equal to 0.05%, S: less than or equal to 0.015%, and P: less than or equal to 0.03%, and has a bulk density of

3.0 + 0.1; and the iron powder meets the following particle size requirements: -60 mesh: more than or equal to 100%, and -100 mesh: more than or equal to 90%; the soda ash comprises Na,COs of more than or equal to 99%, and meets the following particle size requirements: -100 mesh: more than or equal to 100%, and -200 mesh: more than or equal to 98%; and the binder comprises: Na:O: 9.5% to 13.0%, K: less than or equal to 0.050%, and ash: 20.0% to 30.0%; and the binder meets the following particle size requirements: -120 mesh: more than or equal to 100%, and -200 mesh: more than or equal to 50%, wherein the symbol "-" in front of a mesh represents passing through a sieve during screening, for example, "-100 mesh: more than or equal to 100%" means that a proportion of particles that pass through a 100-mesh sieve is greater than or equal to 100%. LU503595

6. A fabrication method of the heat-resistant steel hand welding rod for ultra-supercritical steel CB2 according to any one of claims 1 to 5, characterized by comprising weighing the powders of the flux coating according to the proportions, and uniformly mixing the components; adding water glass, uniformly stirring a resulting mixture in a wet state, and pressing the mixture into a cake; transferring the cake to a coating machine, and wrapping the cake around the special alloy cored wire; and baking a resulting article at 60°C to 100°C for 1 h and then at 350°C to 380°C for 1 h, furnace-cooling to 100°C to 150°C, and taking out the article.

7. The fabrication method of the heat-resistant steel hand welding rod for ultra-supercritical steel CB2 according to claim 6, characterized in that the water glass is used in an amount of 14% to 28% based on a total weight of the components of the flux coating.

8. The fabrication method of the heat-resistant steel hand welding rod for ultra-supercritical steel CB2 according to claim 6, characterized in that the water glass comprises potassium and sodium in a ratio of 1:1.